Re: [PATCH 8/9] clocksource: Improve unstable clocksource detection

[Peter Zijlstra]

On Tue, Sep 01, 2015 at 03:35:18PM -0400, Steven Rostedt wrote:
> On Tue, 1 Sep 2015 11:14:17 -0700
> Shaohua Li <shli@xxxxxx> wrote:
> 
> > > You think that blocking softirq execution for 42.9 seconds is normal?
> > > Seems we are living in a different universe.
> > 
> > I don't say it's normal. I say it's not hard to trigger.
> > 
> > > > it's just VM off. A softirq can hog the cpu.
> > > 
> 
> Please provide a test case that shows the softirq hogging the cpu for
> over 40 seconds.

Do not overlook the MAX_SOFTIRQ_* logic while you're there trying to
explain this ;-)

A softirq running significantly longer than 2 jiffies and not falling
back to ksoftirq is a plain bug.
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